Orthodontic treatment involves repositioning misaligned teeth to provide an improved appearance, bite relation, and masticating function. Repositioning teeth is accomplished by applying precision-controlled external forces to the teeth over a period of time. Orthodontists typically use one of the two types of dental appliances to exert forces on the teeth, namely fixed appliances and removable appliances.
Fixed appliances consist of brackets, bands, arch wires, and accompanying ligatures or elastomeric rings. The brackets are bonded to the surface of the teeth. Ligatures or elastomeric rings are used to fix the arch wires to the brackets. The primary forces used to induce teeth movement are applied through the arch wires. Periodic adjustments and alterations of arch wires are needed to upgrade the precision and strength of the fixed appliance. Although conventional fixed appliances are effective, they are inconvenient to the patient for several reasons. For example, fixed appliances are usually uncomfortable and unattractive as the arch wires are visible during casual interaction. Moreover, with fixed appliances, maintaining normal oral hygiene is difficult, and improper maintenance can lead to various oral diseases.
In order to avoid visible placement of arch wires on the facial surface of the teeth, the arch wires are sometimes placed on the lingual side of the teeth. Although some progress has been made with lingual placement of the arch wires, the small inter-bracket span, the inaccessibility, and the difficulty to adjust the arch wires make its use complicated. Thus, the lingual placement is mostly used in simple and limited cases that involve minor tooth movement.
Removable appliances offer an alternative to the traditional fixed appliances. Minimal visibility during casual interactions is one of the main benefits of removable appliances. Patients generally prefer removable appliances over fixed appliances, because fixed appliances are considered unsightly and are mostly used for adolescences. Earlier versions of removable appliances utilized loops, finger extensions and hooks to anchor the teeth, while exerting pressure on the teeth through contacting surfaces. Recently proposed removable appliances use plastic retainers with finger springs embedded on the lingual side of the teeth surface. These appliances may not be a viable option for patients who need major teeth movement.
In a different approach, systems and methods have been developed using rigid plastic positioning appliances that cover the entire teeth surface. A series of retainers are used to gradually move the teeth to the desired position. The force required to move the teeth relies on the stiffness of the retainer. Several methods have been proposed to use computer software to generate a three-dimensional model of a patient's dentition and subsequently predict the course of treatment based on the model. However, the computerized prediction is not always accurate, because the variableness of teeth movement in the entire arch cannot be accurately determined with one impression alone. Moreover, the skeletal and dental growth of adolescences is generally unpredictable. As a result, the patient may need to undergo a “refinement” procedure at an additional cost, even though the effectiveness of the refinement procedure is uncertain. Furthermore, the removable appliances may not always fit the patient's mouth properly, causing pain or discomfort. This discomfort is often misconstrued for the effectiveness of the appliance. This method has yet to be widely used due to lack of effectiveness and the high cost involved in the process.
Therefore, there is a need for a method and appliance in the orthodontic field for repositioning teeth that is comfortable to use, aesthetic, and provides effective orthodontic therapy, while reducing the amount of laboratory work required and the cost associated with expensive computer software.